Often a door or other closure may be left open unintentionally after use, such as a refrigerator door, or a door may be left closed unintentionally, such as a door over a ventilator opening. It may be costly or undesirable for many types of closures to remain open after use, and it is, therefore, desirable to provide a mechanism for automatically closing the opened door or opening the closed door. Such closures include sliding doors as in a patio door or a commercial refrigerator door, hatches, stereo cabinets, swing doors, sash windows, or any closure movable from either an open position to a closed position or vice versa.
One type of closure for which a self return mechanism is particularly desirable is a sliding door often used for commercial refrigerator and refrigerated display cases. Commercial refrigerators and refrigerated display cases are employed in markets, food-vending operations and the like for the simultaneous preservation of freshness and attractive display of foodstuffs to the customer. Typically, commercial display cases have frames around an opening in a display case with tracks for supporting and guiding large sliding doors which incorporate large areas of multiple layered glazing to permit the customer to see, select and access the refrigerated product easily, while preventing a heat loss into the refrigerated space.
The customer may view the foodsruff in the refrigerator which they wish to purchase, open the sliding door to the refrigerated area, and remove the foodstuff the customer wishes to purchase. Occasionally, the customer may forget to close the sliding door to the refrigerated area. When the sliding door is left open, large amounts of heat are let into the refrigerated section, possibly leading to the spoilage of the foodstuffs while reducing the efficiency of the refrigerator and wasting valuable energy in maintaining the coolness of the refrigerated section. Often, a refrigerated section door that is not closed may remain open for a relatively long period of time if business is slow and employees of the store do not find the opened door.
Assemblies for automatically closing a sliding door are well-known in the art. However, automatically returnable sliding doors have design characteristics that can be improved. For instance, conventional sliding door return assemblies return the door at a relatively constant acceleration causing the door to slam shut and possibly not close completely. Further, if the door is opened only partially, the return force developed in the return assembly may not be sufficient to return the door to its fully closed position. The sliding door return assemblies further may be so complex that the sliding door is difficult to remove from its frame structure for service, which makes cleaning of the space between the door and the door frame structure more difficult. In commercial refrigerators and refrigerated display cases, this space must be cleaned on a regular basis to provide an efficient and sanitary unit as well as a clean appearance for customers and inspectors.
Accordingly, a principal object of the present invention is to provide a self return mechanism for a closure which controls the return of the closure from a first position to a second position.
A further object of the present invention is to provide a door return which varies the acceleration and deceleration or rate of return of the door as it is automatically closed, to prevent the door from slamming into the door frame and not closing fully, to fully close the door regardless of how far the door has been opened, and to improve the safety of the door.
Another object of the present invention is to provide a self return mechanism where the rate of return of the door is subtly controlled by the use of a closing mechanism which provides a force capable of decreasing the rate of return of the door when it is automatically closed from its opened position without slamming the door into the door frame and which provides a force sufficient to close the door even when it is opened only partially.
A further object of the present invention is to provide a self return mechanism using varying frictional interaction between a portion of an elastic element and a braking element through which the elastic element passes to vary the rate of return of the door. This interaction could occur, for example, between a latex cord or tube elastic element and a grooved wheel whereby stretching and relaxing of the elastic element varies the frictional interaction between the elastic element and the wheel.
Another object of the present invention is to provide a slider door return system which allows for easy removal and replacement of the door from the door frame structure.
It is yet another object of the present invention to provide a slider door return system which is inexpensive to manufacture and simple to assemble.
It is yet a further object of one embodiment of the present invention to provide a slider door return system having the objects stated above for slanted sliding doors.